Assemblies or packages for filtering fluids introduced therein are well-known in the art. One such package described in U.S. Pat. No. 3,092,249 employs a container made of air impervious material and has therein an opening or mouth closed by an air sterilizing filter so that the only ingress for air to enter the container is through the filter. Another apparatus described in U.S. Pat. No. 4,777,137 employing a complex tubular sleeve, the bottom of which is closed by a sterile microporous member filter sealingly fixed on its periphery to one end of the sleeve is used to collect and filter a liquid sample to be tested. This is done so that the downstream side of the filter can be contacted with a culture medium for purposes of counting living microorganisms contained in the liquid sample. A similar apparatus is described in U.S. Pat. No. 4,640,777. Another assembly described in U.S. Pat. No. 4,702,834 for filtering liquids employs a plastic laboratory filterware comprising upper and lower chambers separated by a neck portion which includes a plastic support plate. A cellulose nitrate filter membrane is ultrasonic welded to the support plate for filtering liquids through the neck portion. The assembly is a bulky rigid structure, however, and is uneconomical for one-time use. Another pre-sterilized bag assembly in association with a sterilizing microporous filter described in U.S. Pat. No. 4,964,261 employs a flexible sterile tubular bag with a single inlet for introducing sterile solutions but the microporous filter is located outside of the bag.